1. Field of the Invention
The present invention relates to a light emitting tube array and a display device employing the light emitting tube array and, particularly, to a plasma tube array including a plurality of elongated plasma tubes and adapted to be driven by electrodes provided outside the plasma tubes.
2. Description of the Related Art
An elongated glass tube having a fluorescent layer provided therein and filled with a discharge gas with opposite ends thereof sealed is generally called “light emitting tube” or “plasma tube”. A display panel including a multiplicity of such plasma tubes regularly arranged, a plurality of transparent display electrodes provided on a front side thereof as extending perpendicularly to the plasma tubes and data electrodes (address electrodes) provided on a back side thereof as extending parallel to the plasma tubes is generally called “plasma tube array” or “PTA”. In the PTA, electric discharge is caused by applying operating voltages to the display electrodes and the data electrodes, and UV radiation generated by the electric discharge excites a fluorescent material, which in turn emits visible light for display (see, for example, JP-A-2000-315460).
The PTA is configured such that the plasma tubes are sandwiched between a front plate formed with the display electrodes and a rear plate formed with the address electrodes and combined with the front plate and the rear plate by an adhesive tape or an adhesive agent. Therefore, the PTA is a very light and flexible display device.
In principle, the display size of the PTA is determined by the length and number of the plasma tubes. Therefore, the PTA is more advantageous than existing display devices (PDPs and LCDs) to provide a large-scale display panel.
A known technique for improving the brightness of the PTA is to increase contact areas between the plasma tubes and the display electrodes provided on the front plate (see, for example, JP-A-2003-86142).
Further, a known technique for stabilizing the driving voltages is to use a flexible sheet such as a resin film as the front plate and to reduce the influence of variations in the sectional shapes of the plasma tubes (see, for example, JP-A-2003-297249).
While the display size of the PTA is determined by the number of the plasma tubes (light emitting tubes) as described above, the PTA (light emitting tube array), which generally includes several thousands of plasma tubes, suffers from variations in the sectional shapes and the sectional sizes of the plasma tubes.
In the PTA (disclosed in JP-A-2000-315460) which includes the plasma tubes T sandwiched between the front plate Ff provided with the display electrodes Ed and the rear plate Fr provided with the address electrodes Ea as shown in FIG. 8, a thin flexible sheet is used as the front plate Ff to accommodate the variations in the sectional shapes of the plasma tubes T so that the display electrodes Ed are kept in intimate contact with the light emitting tubes T.
Even with such a construction, the PTA suffers from uneven display (uneven brightness), because the contact areas between the display electrodes Ed and the plasma tubes T differ depending on the sizes of the plasma tubes T as shown in FIG. 8.